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# Category Archives: math

## Four color theorem: A fast algorithm – 2

https://4coloring.wordpress.com/2016/10/16/four-color-theorem-a-fast-algorithm These are the OLD and NEW (last column) execution times on my new laptop: 100 – 196 vertices, 294 edges = 0 seconds – 0 seconds 200 – 396 vertices, 594 edges = 1 seconds – 0 seconds 300 – 596 vertices, 894 edges = … Continue reading

## I moved the code under github

I moved all code under github here: https://github.com/stefanutti I organized the folders a little betters (different github repos) I’m experimenting docker to deliver & deploy the Java and Python software I’ll also try to integrate a deep learning module, based on … Continue reading

## Four color theorem: about edges selection

For the decomposition of a graph representing a map, I’m trying to use different algorithms to select the edge to remove. The question is: When you have multiple valid choices, which is the best edge to select … if any? Some basic … Continue reading

## Four color theorem: new ideas

This is what I want to try: Select an F2, F3 or F4 preferably when it is near an F5 and remove the edge that joins the two faces Analyse also the balance of the Euler’s identity when removing edges, to … Continue reading

## Four color theorem: what next?

The algorithm I use to color graphs works pretty well … BUT: Sometimes (very rarely) it gets into an infinite loop where also random Kempe color switches (around the entire graph) do NOT work. The good is, if I reprocess … Continue reading

Posted in math
Tagged 4 color theorem, coloring, four color theorem, Kempe, Kenneth Appel
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## Four color theorem: Infinite switches are not enough – Rectangular maps :-(

I transformed the really bad case into a rectangular map to play with the Java program and Kempe random switches. Here is the graph with the two edges to connect: The two edges marked with the X, have to be … Continue reading